3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8
th
UNIT LOAD
DECEMBER 2009
REV. 1.0.0
GENERAL DESCRIPTION
The
XR3170E - XR3178E
family of RS-485 devices
are designed for reliable, bidirectional communication
on multipoint bus transmission lines. Each device
contains one differential driver and one differential
receiver.
XR3172E, XR3175E
and
XR3178E
are half-
duplex devices; other part numbers are full-duplex.
All devices comply with TIA/EIA-485 and TIA/EIA-422
standards. Lead free and RoHS compliant packages
are available for all models.
These devices are ruggedized for use in harsh
operating conditions over the entire common-mode
voltage range from -7V to +12V. Receivers are
specially designed to fail-safe to a logic high output
state if the inputs are left un-driven or shorted. All RS-
485 bus pins are protected against severe ESD
events up to +/-15kV (Air-Gap and Human Body
Model) and up to +/-8kV Contact Discharge (IEC
61000-4-2). Drivers are protected from excess
current flow caused by bus contention or output
short-circuits by both an internal current limit and a
thermal-overload shutdown. Devices are rated for
Industrial (-40 to +85°C) operating temperatures.
Receivers have exceptionally high input impedance,
which places only 1/8
th
the standard load on a shared
bus. Up to 256 transceivers may coexist while
preserving full signal margin.
All devices operate from a single 3.3V power supply
and draw negligible quiescent power. All versions
except the XR3171E, XR3174E and XR3177E may
independently enable and disable their driver and
receiver and enter a low power shutdown mode if
both driver and receiver are disabled. All outputs
maintain high impedance in shutdown or when
powered off.
F
IGURE
1. T
YPICAL
A
PPLICATION
C
IRCUIT
DE
XR3178E
B
DI
A
RO
B
XR3178E
A
R
T
FEATURES
•
3.3V Single Supply Operation
•
High Speed 20Mbps Data Rate
•
Slew Rate Limited - 250kbps And 500kbps Data
Rate
•
1/8
th
Unit Load, 256 Transceivers On Bus
•
Enhanced Failsafe For Receiver - Open, Short Or
Terminated Lines
•
Robust ESD Protection For RS-485 Pins
■
■
■
+/-15kV Air-Gap Discharge
+/-15kV Human Body Model
+/-8kV Contact Discharge
•
Hot Swap Glitch Protection
•
Driver Short Circuit Current Limit And Thermal
Shutdown For Overload Protection
•
Ultra-Low 650uA Quiescent Current
•
1
µ
A Shutdown Mode
•
Industry Standard Package Footprints
TYPICAL APPLICATIONS
•
Motor Control
•
Building Automation
•
Security Systems
•
Remote Utility Meter Reading
•
Long Or Un-Terminated Transmission Lines
DE
XR3178E
B
STUB
R
T
DI
A
RO
B
XR3178E
A
RE
RE
DE
RE DE
DI
RO
DI
RO
RE
Exar
Corporation 48720 Kato Road, Fremont CA, 94538
•
(510) 668-7000
•
FAX (510) 668-7017
•
www.exar.com
XR3170E-3178E
3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8
th
UNIT LOAD
F
IGURE
2. P
IN
O
UT
A
SSIGNMENT
REV. 1.0.0
RO
RE
DE
DI
1
2
3
4
8-Pin NSOIC
Half Duplex
XR3172E
XR3175E
XR3178E
8 VCC
7 B
6
A
5 GND
VCC
RO
DI
GND
1
2
3
4
8-Pin NSOIC
Full Duplex
XR3171E
XR3174E
XR3177E
8
7
6
5
A
B
Z
Y
NC
RO
RE
DE
DI
GND
GND
ORDERING INFORMATION
P
ART
N
UMBER
XR3170EID
XR3171EID
XR3172EID
XR3173EID
XR3174EID
XR3175EID
XR3176EID
XR3177EID
XR3178EID
1
2
3
4
5
6
7
14-Pin NSOIC
Full Duplex
XR3170E
XR3173E
XR3176E
14 VCC
13 NC
12 A
11 B
10 Z
9
8
Y
NC
P
ACKAGE
14-pin Narrow SOIC
8-pin Narrow SOIC
8-pin Narrow SOIC
14-pin Narrow SOIC
8-pin Narrow SOIC
8-pin Narrow SOIC
14-pin Narrow SOIC
8-pin Narrow SOIC
8-pin Narrow SOIC
O
PERATING
T
EMPERATURE
R
ANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
D
EVICE
S
TATUS
Active
Active
Active
Active
Active
Active
Active
Active
Active
Note: Please visit www.exar.com for tape and reel option part numbers.
2
XR3170E-3178E
REV. 1.0.0
3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8
th
UNIT LOAD
PIN DESCRIPTIONS
Pin Assignments
P
IN
N
UMBER
H
ALF
D
UPLEX
XR3172E
XR3175E
XR3178E
1
F
ULL
D
UPLEX
XR3171E
XR3174E
XR3177E
2
XR3170E
XR3173E
XR3176E
2
P
IN
N
AME
T
YPE
D
ESCRIPTION
RO
O
Receiver Output. When RE is low and if (A-
B)
≥
-50mV, RO is High. If (A-B)
≤
-200mV,
RO is Low.
Receiver Output Enable. When RE is Low,
RO is enabled. When RE is High, RO is
high impedance. RE should be High and
DE should be low to enter shutdown mode.
RE is a hot-swap input.
Driver Output Enable. When DE is High,
outputs are enabled. When DE is low, out-
puts are high impedance. DE should be low
and RE should be High to enter shutdown
mode. DE is a hot-swap input.
Driver Input. With DE high, a low level on DI
forces Non-Inverting output low and invert-
ing output high. Similarly, a high level on DI
forces Non-Inverting output High and Invert-
ing output Low.
Ground.
Non-Inverting Receiver Input and Non-
Inverting Driver Output.
Inverting Receiver Input and Inverting
Driver Output.
+3.3V power supply input. Bypass with
0.1uF capacitor.
Non-Inverting Receiver Input.
Inverting Reciever Input.
Non-Inverting Driver Output.
Inverting Driver Output.
No Connect, not internally connected.
2
-
3
RE
I
3
-
4
DE
I
4
3
5
DI
I
5
6
7
8
-
-
-
-
-
4
-
-
1
8
7
5
6
-
6, 7
-
-
14
12
11
9
10
1, 8, 13
GND
A
B
Vcc
A
B
Y
Z
NC
Pwr
I/O
I/O
Pwr
I
I
O
O
-
Pin type: I=Input, O=Output.
3
XR3170E-3178E
3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8
th
UNIT LOAD
REV. 1.0.0
ABSOLUTE MAXIMUM RATINGS
These are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections to the
specifications below is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability and cause permanent
damage to the device.
V
CC
Input Voltage at control pins (RE, DE and DI)
Driver Output Voltage (A, B, Y and Z)
Receiver Output Voltage (RO)
Receiver Input Voltage (A and B)
Storage Temperature Range
Lead Temperature (soldering, 10s)
Package Power Dissipation
Maximum Junction Temperature 150°C
8-Pin SO
θ
JA
= 128.4°C/W
14-Pin SO
θ
JA
= 86°C/W
+6.0V
-0.3V to (V
CC
+ 0.3V)
-8V to +13V
-0.3V to (V
CC
+ 0.3V)
-8V to +13V
-65°C to + 150°C
+300°C
CAUTION:
ESD (Electrostatic Discharge) sensitive device. Permanent damage may occur on unconnected devices subject to high energy electrostatic fields. Unused
devices must be stored in conductive foam or shunts. Personnel should be properly grounded prior to handling this device. The protective foam should be
discharged to the destination socket before devices are removed.
ELECTRICAL CHARACTERISTICS
U
NLESS OTHERWISE NOTED
: V
CC
= +3.0V
TO
+3.6V
WITH
T
A FROM
-40
O
C
TO
+85
O
C. T
YPICAL VALUES ARE AT
V
CC
= +3.3V
AND
25
O
C.
S
YMBOL
P
ARAMETERS
M
IN
.
TYP.
M
AX
.
U
NITS
C
ONDITIONS
DRIVER DC CHARACTERISTICS
V
OD
Differential Driver Output
2.0
1.7
1.7
1.7
∆V
OD
Change in Magnitude of Differential
Output
-0.20
-0.20
-0.20
2.65
2.35
2.35
2.35
0.20
0.20
0.20
V
Vcc
V
No Load
R
L
= 100Ω (RS-422), Figure 3
R
L
= 54Ω (RS-485), Figure 3
V
CM
= -7V, Figure 4
V
CM
= +12V, Figure 4
R
L
= 100Ω (RS-422), Figure 3,
See Note 1
R
L
= 54Ω (RS-485), Figure 3,
See Note 1
V
CM
= -7V, Figure 4, See
Note 1
-0.20
V
OC
Driver Common Mode Output
Voltage steady state
0.20
3.0
V
V
CM
= +12V, Figure 4, See Note
1
Figure 3
4
XR3170E-3178E
REV. 1.0.0
3.3V HIGH SPEED RS-485/RS-422 TRANSCEIVERS WITH 1/8
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